Piston



June 3, 1930. J. A. DUNNING PISTON Filed Sept. 23. 1929 2 Sheets-Sheet 1 Inventor 1762/7266 A: .Dunnc'nfi Bygg Patented June 3, 1930 UNITED STATES PATENT OFFICE- J'AMES A. D'UNNIN G, OF SUFFOLK, VIRGINIA, ASSIGNOR OF ONE-THIRD TO VERNON S.

MAYBERR'Y, F PORTSMOUTH, VIRGINIA OF ROCKY MOUNT, NORTH CAROLINA AND ONE-THIRD TO CARSON S. DUNNING,

f PISTON Applicationfiled September 23, 1929. Serial No. 394,513.

The present invention relates to a piston designed particularly, although not necessarily, for internal combustion engines.

The prime object of the invention resides in the provision of a piston having a construction aifordingexpansion by means of a plurality of semi-cylindrical segments with proper means tending to push such segments outwardly into engagement with the wall of a cylinder, together with suitable joint valves, forthe purpose of preventing the, passage of gases between the piston and the wall of the cylinder, thereby eliminating the necessity of using packing rings.

Another very important object of the invention resides in the provision of a piston with a much larger area of expansive surface and greater range of expansion which willafford eflicient compression and vacuum seal with less wall friction than the conventional ring piston, thereby maintaining its eificiency longer and with less wear than the ring piston; its construction also providing balanced upper and lower resistance lengthwise the piston as against the oblique thrust of the connecting rod, thereby preventing piston sla l d ith the above objects in view, the invention resides in certain novel features of construction and in the combination and arrange- .ment of parts as will hereinafter be morefully described and claimed.

Inthe drawings Figure 1 is a side elevation of a iston embodying the features of the invention.

Figure 2 is a vertical sectional view of Figure 1.

Figure 3 is a horizontal section through segments and core taken approximately on the line 33 of Figure .1.

Figure 4 is a detail perspective view of a wrist pin.

Figure 5 valve. 1

Figure 6 is a side elevation taken 3 angles to Figure 1. v

' Figure 7 is a vertical sectional view of Figure 6. j v g Figure 8 is a plan view of the upper head is a detail perspective.view of a at right 59, 61 cap.

be seen that the numeral 10 denotes an ocscrew; with upper side beveled to provide clearance for the spring disc.)

Figure 9 is a top plan view of the spring disc mounted on the piston, a portion thereof being broken away to show the seal plate.

Referring to the drawings in detail, it will tagonal' core with four plane and four curved faces and a circular flange 11 having a skirtlike projection 12 in which end is formed a cavity 13 for the connecting rod, which end I shall hereinafter refer to as the bottom end for convenience only.

Near the middle portion, the core is provided with diametrically extending bores in which a hollow wrist pin 14 is mounted to extend across the cavity 13 and a conventional or any preferred type of connecting rods 15 is rockably engaged thereon in the usual well known manner.

A safety type set screw 16 is threaded through the core 10 from the upper end of the core and has a reduced end projecting into an opening 16 provided near one end of the wrist pin 11 so as to prevent movement of the wrist pin with respect to the core. Indentations 17 at the end of the wrist pin serve to seat a wrench forrotating the wrist pin to correct position.

A reduced threaded extension 18 is formed at theupper end of the core 10 and has threadably engaged thereon a head 19 which is locked against rotation by a cotter pin 20 or other suitable means.

The head 19 is formed with an inner circular walled recess 21 or housing a thin annular spring disc 22 which is fitted to slip over the threaded extension 18 of the core 10.

Thespring disc 22 is formed flat paralleling the contact of the washers 23 and 24 on either side, then slightly angled toward the rim, then reverting toform a slightly curved thickened rim which presses against a corresponding seat on the seal plate 25. (The lower washer should be large enough to extend part way over the set screw ,16 to lock said set The seal'plate 25 is a com aratively thin disc-of the same diameter as t e head 19 with an opening shaped to fit and slip over the Octagonal end of the core 10, one side wlth of segments and the other side shaped to seat the curved. rimof the spring disc 22 and shoulderedto underlap the projection of the head 19; thereby providing, when all the parts are properly fitted and assembled, a pressing butflexible contact of all transverse abutmentsbetween the spring disc and the lower head 11 of the core 10. (Gas pressure entering the aperture between the head and the seal plate tends to augment the pressure of the spring disc and cannotpass beyond it into the interior of thepistom) 1he wall of the piston-is formed of three pairs of semi-cylindrical segments 26 fitted to slip over and register with the correspondmg planes of the core 10 to insure diametrical movement of the'segments and to prevent lateral play of the segments in respect to the core.

All the segments are identical in size and construction and have their abutting edges formed with inner' beveled indentations to receive and seat the valves 27 provided for sealing the joints interiorly, the valve recess being extended circumferentially by a thin slot 28 to form flexible flaps on either sideof the joints, the ends of these flaps resting upon an oblong compressed coil spring 29 seated within a cavity 30 in valve 27, the tension of? the spring tending to press the valve inwardone quarter ofv the circumference of the circle posed at'right angles.

' to. correspond to the circumferential slots,

to avoid communication withthe slots in the opposing pairs of segments which are dishe valve 27 's formed with'parallel'ends fitted to register with the transverse faces of the segments, with" longitudinal faces cor-' responding to and registering with' 'the angular abutments on either s'ideofthe joint and intersected by a plane parallel to: the core but separated from'the core by: sufiicient space to provide for inner movement to compensate for wear; the top side being formed with an oblong cavity for housing the spring 29. The foregoing is illustrated most clearly in Figures 3 and 5 of the drawing,

Circular walled sockets 31 are centrally located within the middle planes-of the'seg ments 26 in 'which'are housed compressed coil "springs'32 the "ends of which impinge against the bottom of the socketsand thefopposingf planes of the core '10, tending to spread-the the piston may be 7 g i l t away frofngthe core Ifrprn 'eachl The? second 501- middle is likewise assembled, but isposed diametri-' cally at right angles to the first pair, and

other against thewall of the 'cyliii" er'i-n wh disposed. Suflicient clearance must oil grooves 33 be pitividiid be tween the core 10 and the opposing planes of the segments, and between the abutting ends 4 of the flaps, and between the valves and the flaps to permit expansion to be absorbed by the springs; likewise, similar clearance must be provided in fitting the heads and the seal plate; thereby permitting exact fitting of the expanding portionof the piston without danger of the piston sticking in the cylinder or generating. excessive wall friction.

enough to insure efficient seal of all the transverse joints; while the pressure of the coil springs must be suificient to overcome the braking effect of the spring disc together with minimum excess to provide efiicient seal between the piston and the cylinder wall.

The sequence of such transverse pressures ments being that the pressure of the se to the COIltIfiCtlOIl in circumference of the piston is braking effect of the spring The spring disc pressure must be strong likewise increased. The fluctuating difi'erences'in expansion as between the piston and the cylinder wall'being in such manner ab-- sorbedby the springs, agfitting contact is thereby maintained with minimum frictional resistance.

' Requisite tension of the springs must need be determined by experiment; and, byreason' of the restricted space, adequate tension with maximum resiliency could best be attained with spring material of flat shape and oval edge; also, it must be-of such character as will withstand the prevailing high temperatures without deterioration of elasticity; this qualification likewise applying for t e spring disc. (Probably Monel metal or some similar nickel alloy would be well adapted for the purpose.) The segments are provided with encircling located vaway from the transverse joints 34 in order to avoid commun ca-' tion circumferentially between the longitudinal joints.

In assembling the. piston, the'wr st pin 14 is inserted through the 'bores'and, the connecting rods 15 and fastened with the lock screw 16.

' The segments 26 inay then beas'sembled I bout the 001E710; beginning at the lower posed with the joints transverse 'in relation to the wirst pin and pressedtogether and asuitableretaining band"(not shown) disj head, with the coil springs 32 inserted in the "sockets 31, the first pair of-segments is discai ities -30, theii'ralves 27 may be entered and air of segments pressed into their places, bridging the joints.

retaining band slipped up to engage over all the segments; then the valves and their springs pressed into their places, as with the others.

The seal plate 25 is then slipped on to the end of the core 10, with the plane face abutting against the segments; then the larger washer 24 with the beveled side up; then the spring disc 22 with the rim against its seat on the seal plate, followed by the smaller washer 23 and last, the head T9 is screwed on hard up against the Washer, thereby imparting tension to the spring disc and se-. curely closing all apertures surrounding the threaded extension of the core 10 and all joints both transverse and longitudinal.

The hole for the cotter pin is then drilled and the cotter pin inserted and fastened, locking the head against displacement.

The piston may now be slipped into the cylinder and of course, the retaining band will be forced oif the piston as will be quite apparent. The band must be used also for removing the piston from the cylinder.

It is believed that the many advantages of a piston constructed in accordance with this invention Will be readily understood and although the preferred embodiment of said invention is as illustrated and described, it is to be understood that changes in the details of construction may be had which will fall within the scope of the invention as claimed.

What is claimed is L A piston of the character describedcomprising a core. a circumferentially extending head on the lower end of the core, substantially semi-circular separable segments encircling the core and mounted on the head, expansible springs positioned between the segments and the core and resilient means mounted on said core for yieldingly urging the segments against the head.

2. A piston ring of the character described comprising a core having connected lane and arcuate side portions, a circum erentially extending head on the lower end thereof, a plurality-of superposed pairs of substantially semi-circular segments incircling the core and mounted on the head, expansible springs between the .core and the segments, a threaded extension on the upper end of the core of less diameter than said core, an annular sealing ring on the adjacent segments having an inclined upper face, a resilient disc encircling the extension with its peripheral ortion enga ing the inclined face of the sea ing ring an means mounted on the extension for engagement with the disc for maintaining the same under tension on the sealing ring for urging same, together with the segments toward the head.

3. A piston of the character described comprising a core having connected lane and arcuate side portions, a circum erentially extending head on the lower end thereof, a plurality of superposed pairs of substantially semi-circular segments encircling the, core and mounted on the. head, expansible springs between the core and the segments,

the adjacent end of each pair of segments being provided with opposed recesses having an arcuate front wall and a beveled rear Wall and being further provided with a circumferentially extending slit communicating with the recesses providing a yieldable tongue on each end of the segments a substantally Wedge-shaped valve extending into the opposed recesses and having a socketed forward face, an expansible spring seated in the socket and engaging the adjacent end portions of the flaps for urging the same outwardly, and resilient means mounted on the core for urging the segments toward the head.

In testimony whereof I aflix my signature.

a JAMES A. DUN NING. 

